1. Field of the Invention
The present invention relates to optical encoder components, and more specifically, it relates to reflective code-wheel disc optical encoder manufacturing technology
2. Description of Related Art
Rotary encoders fulfill a multitude of consumer and industrial applications from acting as infinitely rotating dials on stereos and other human input devices to acting as feedback loops for motors that drive equipment demanding positional accuracy. There are a variety of styles of rotary encoder which are established as prior art. While some encoders utilize mechanical contact mechanisms similar to that of a brushed motor in order to send varying signals to a device, others utilize magnetic fields to send constantly varying analog signals as an output. The style of encoder discussed herein is a third type referred to an optical encoder, which is a device that utilizes a lighting source, a code wheel disc and a sensor to decipher the interruptions of the lighting source that are established during its interaction with the code wheel disc. Of optical encoders, there are two common types that establish the prior art. One of these types is a transmissive system that locates the light source on one side of a code wheel disc and the sensor on the other side of the code wheel disc. In this style of optical encoder, the code wheel disc may be a translucent mylar with opaque markings on its surface to block the transmission of the light source through the substrate, or it may be another mechanism such as an opaque plastic disc with cut-away gaps that allow the light signals to transmit through the gaps effecting the sensor. Another common type of optical encoder is that of the reflective code-wheel disc optical encoder, which employs a code-wheel disc which has a series of reflective and non-reflective patterns on its surface. Opposite that surface are both the light source and the sensor, arranged in a way in which the light source focuses on the surface of the code wheel disc in a fashion that reflects back toward the sensor when the wheel is oriented in a position where the reflective sections of code pattern interact with the light source. The pattern which is chosen in any optical rotary encoder can provide either an incremental or absolute position of the shaft to which the encoder codewheel is attached. FIG. 1 shows a prior art reflective code wheel design. A reflective mylar code-wheel disc 16 is embedded between glass discs 12 and 14. Reflective codewheel disc 16 is attached to hub 18 via retaining washer 10.